Fernando Alonso's plans to contest his third Indy 500 this May are reportedly in tatters.

We reported last week that the Spaniard had agreed to make his latest attempt to complete the 'triple crown' with Michael Andretti's top outfit.

An announcement was apparently imminent, but new reports indicate that the deal has now been vetoed by Andretti's engine supplier Honda.

Alonso and Honda have a checkered past, with the former two-time F1 champion now admitting that he regrets describing the Japanese company's engine supplied to McLaren in 2015 as a "GP2 engine".

READ | Regret comes too late - Alonso sorry for comparing F1's McLaren to a GP2 car

"Maybe I shouldn't have said it, but I didn't say it in the TV pen or the press conference," he told F1 Racing magazine.

"If a top driver today went through the performance that I went through, I could not imagine what they would say," added Alonso, 38.